U.S. patent number 10,005,088 [Application Number 15/389,619] was granted by the patent office on 2018-06-26 for flotation of sphalerite from mixed base metal sulfide ores either without or with largely reduced amount of copper sulfate addition using 2-(alkylamino)ethanethiols as collectors.
This patent grant is currently assigned to LAKEHEAD UNIVERSITY. The grantee listed for this patent is Lakehead University. Invention is credited to Inderjit Nirdosh, Natarajan Ramanathan.
United States Patent |
10,005,088 |
Nirdosh , et al. |
June 26, 2018 |
Flotation of sphalerite from mixed base metal sulfide ores either
without or with largely reduced amount of copper sulfate addition
using 2-(alkylamino)ethanethiols as collectors
Abstract
The main objective of the invention was to develop a new
flotation collector that could eliminate or reduce the amount of
copper sulfate used in the flotation of sphalerite. Different
series of collectors such as cupferrons, arylhydroxamic acids and
amino mercaptans or amino thiols were synthesized and tested. Amino
mercaptans/aminothiols were found to be very effective in floating
sphalerite from a lead-zinc ore using only 10-15% of copper sulfate
used with conventional xanthate collector. The present invention
does not require any alteration in the current mill practices. This
warrants only changing the flotation collector in zinc flotation
stage from, for example, potassium amyl xanthate (PAX) to the new
collector.
Inventors: |
Nirdosh; Inderjit (Thunder Bay,
CA), Ramanathan; Natarajan (Trichy, IN) |
Applicant: |
Name |
City |
State |
Country |
Type |
Lakehead University |
Thunder Bay |
N/A |
CA |
|
|
Assignee: |
LAKEHEAD UNIVERSITY (Thunder
Bay, ON, CA)
|
Family
ID: |
59351212 |
Appl.
No.: |
15/389,619 |
Filed: |
December 23, 2016 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20170209873 A1 |
Jul 27, 2017 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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62281872 |
Jan 22, 2016 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B03D
1/02 (20130101); C22B 1/24 (20130101); B03D
1/01 (20130101); C22B 3/00 (20130101); B03D
1/012 (20130101); B02C 23/08 (20130101); B03D
2201/02 (20130101); B03D 2203/02 (20130101) |
Current International
Class: |
C22B
1/24 (20060101); C22B 3/00 (20060101); B03D
1/01 (20060101); B02C 23/08 (20060101) |
Foreign Patent Documents
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1084178 |
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Aug 1980 |
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CA |
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1265876 |
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Feb 1990 |
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CA |
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Primary Examiner: Swain; Melissa S
Attorney, Agent or Firm: Williams; Michael R. Dupuis; Ryan
W. Ade & Company Inc.
Parent Case Text
PRIOR APPLICATION INFORMATION
The instant application claims the benefit of U.S. Provisional
Patent Application 62/281,872, filed Jan. 22, 2016.
Claims
The invention claimed is:
1. A method for flotation of zinc-containing ore for mixed base
metal ore comprising: grinding a quantity of mixed base metal ore,
said mixed base metal ore comprising lead-zinc ore and/or
copper-zinc ore; adding water and a frothing agent to the ground
ore, thereby forming a ground ore solution; adding a lead collector
solution and/or a copper collector solution; collecting floated
lead ore and/or copper ore from the ground ore solution; adding a
zinc collector, said zinc collector having a chemical structure
according to compound (6): ##STR00011## wherein: R.sup.1=H,
R.sup.2=alkyl, aryl, alkoxy; or R.sup.1=alkyl, aryl, alkoxy;
R.sup.2=H; or R.sup.1=R.sup.2=alkyl; and y=2 or 3; and collecting
the zinc-containing ore.
2. The method according to claim 1 wherein the zinc collector has a
chemical structure according to compound (5): ##STR00012## wherein
x is an integer between 2 and 12.
3. The method according to claim 2 wherein x is between 2 and
9.
4. The method according to claim 2, wherein x is 2.
5. The method according to claim 2, wherein x is 5.
6. The method according to claim 2, wherein x is 9.
7. The method according to claim 1 wherein the zinc collector is in
the form of a water-soluble salt.
8. The method according to claim 1 wherein the zinc collector is in
the form of an amine salt.
9. The method according to claim 1 wherein the zinc collector is
added in an amount of at least 300 g/tonne of ore.
10. The method according to claim 1 including adjusting the pH of
the ground ore solution to below 7 prior to adding the lead
collector solution.
11. The method according to claim 1 including adjusting the pH of
the ground ore solution to about 6 prior to adding the lead
collector solution.
12. The method according to claim 1 including adding copper sulfate
in an amount at least 100 g/tonne of ore after addition of the lead
collector solution and/or the copper collector solution.
Description
FIELD OF THE INVENTION
The present invention relates to the field of mineral processing.
More specifically, the present invention relates to the
pre-concentration of zinc ores using forth flotation.
BACKGROUND OF THE INVENTION
Froth flotation is a pre-concentration process extensively used in
processing low-grade ores. Effective pre-concentration operations
concentrate most of the valuable mineral into a small mass and thus
reduce equipment sizes, chemical consumption and material handling
in subsequent stages. In the current industrial practice of
concentrating lead-zinc ores using froth flotation, first a lead
mineral (galena) is pre-concentrated in stage-1 as lead-rougher
(Pb-R) and then in the subsequent stage (Stage-2) the zinc mineral
(sphalerite) is concentrated as the zinc-rougher (Zn-R). In order
to avoid any sphalerite coming into the Pb-R stage, it is
suppressed by adding reagents such as sodium metabisulfite (MBS),
sodium cyanide and zinc sulfate. Galena, the lead mineral, is
floated using potassium ethyl xanthate (PEX) as the collector.
After floating galena, sphalerite suppressed in the Pb-R stage is
activated by copper sulfate and then floated using potassium amyl
xanthate.
Copper sulfate not only activates the sphalerite suppressed in the
Pb-R stage but also facilitates the formation of a more stable
surface complex with the xanthate collector, thereby enabling its
flotation into the froth.
The amount of copper sulfate added depends on the grade of
sphalerite in the ore. Generally, about 1 kg of copper sulfate is
added per tonne of ore. Hence, a mill processing about 20,000
tonnes of ore per day requires 20 tonnes of copper sulfate. It is
of note that zinc in minerals does not form a stable surface
complex with xanthates. Consequently, xanthates by themselves are
not capable of floating the zinc minerals effectively.
Copper ions in copper sulfate added for activation attach to the
zinc sites and form a stable surface complex with the xanthate
collector and thus, copper sulfate performs a dual action of
activating suppressed sphalerite and forming a more stable surface
complex with xanthate.
##STR00001## Generic structure of xanthates.
It is very important to keep the pyrite (the gangue mineral) in the
tailings rather than co-floating into the float concentrate. Pyrite
contamination in the zinc float concentrate reduces the value of
the concentrate and renders it commercially less profitable.
Among the auxiliary chemicals used in a flotation circuit, copper
sulfate is the most expensive and corrosive. The corrosive nature
of copper sulfate reduces the useful life of machinery. Also, the
presence of copper makes mill effluents toxic, meaning that
expensive effluent-treatment is needed before discharge.
Furthermore, the shelf-life of xanthates is limited due to their
decomposition in moist environments, and auto-decomposition of
xanthates produces harmful volatile substances such as carbon
disulfide. Finally, the copper sulfate is unrecoverable for re-use
or recycling and ends up in the effluents.
SUMMARY OF THE INVENTION
According to a first aspect of the invention, there is provided a
method for flotation of zinc-containing ore for mixed base metal
ore comprising:
grinding a quantity of mixed base metal ore, said mixed base metal
ore comprising lead-zinc ore and/or copper-zinc ore
adding water and a frothing agent to the ground ore, thereby
forming a ground ore solution;
adding a lead collector solution and/or a copper collector
solution;
collecting floated lead ore and/or copper ore from the ground ore
solution;
adding a zinc collector, said zinc collector having a chemical
structure according to compound (6):
##STR00002## wherein:
R.sup.1=H, R.sup.2=alkyl, aryl, alkoxy; or
R.sup.1=alkyl, aryl, alkoxy; R.sup.2=H; or
R.sup.1=R.sup.2=alkyl; and
y=2 or 3; and
collecting the zinc-containing ore.
In some embodiments, R.sup.1 and/or R.sup.2 is a C.sub.2-C.sub.12
alkyl, aryl or alkoxy, where appropriate. In other embodiments,
R.sup.1 and/or R.sup.2 is a C.sub.2-C.sub.9 alkyl, aryl or alkoxy,
where appropriate.
According to a further aspect of the invention, there is provided
use of a zinc collector compound, said compound comprising a
chemical structure according to compound (6):
##STR00003## wherein:
R.sup.1=H, R.sup.2=alkyl, aryl, alkoxy; or
R.sup.1=alkyl, aryl, alkoxy; R.sup.2=H; or
R.sup.1=R.sup.2=alkyl; and
y=2 or 3
for flotation of a zinc-containing ore.
In some embodiments, R.sup.1 and/or R.sup.2 is a C.sub.2-C.sub.12
alkyl, aryl or alkoxy, where appropriate. In other embodiments,
R.sup.1 and/or R.sup.2 is a C.sub.2-C.sub.9 alkyl, aryl or alkoxy,
where appropriate.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1: Time-recovery plot using 200 g copper sulfate added per
tonne.
FIG. 2: Time recovery plot using 300 g copper sulfate per
tonne.
FIG. 3: Time recovery plot using 400 g copper sulfate per
tonne.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Unless defined otherwise, all technical and scientific terms used
herein have the same meaning as commonly understood by one of
ordinary skill in the art to which the invention belongs. Although
any methods and materials similar or equivalent to those described
herein can be used in the practice or testing of the present
invention, the preferred methods and materials are now described.
All publications mentioned hereunder are incorporated herein by
reference.
Flotation is universally used to concentrate minerals from
low-grade ores into smaller mass. For sulfide base-metal ores, such
as the lead-zinc sulfide or copper-zinc sulfide ores, xanthates are
used as flotation collectors. In such ores, lead (or copper)
minerals are floated first and zinc minerals are suppressed.
Xanthates are not effective for floating zinc minerals such as
sphalerite. Therefore, after floating lead (or copper), the
addition of copper sulfate is essential to activate the flotation
of sphalerite. Copper sulfate is the most expensive auxiliary
chemical in the flotation circuit, as discussed above.
Described herein is a new flotation collector that floats zinc
minerals without needing copper sulfate. The new collector is very
selective for zinc and does not float much pyrite. Specifically,
described herein are chemical alternatives to the xanthates. The
results, discussed below, indicate that the addition of copper
sulfate is either completely eliminated or drastically reduced to
less than 10-20% of the usual amount needed. This is unavoidable
because of the suppression of zinc minerals in the earlier
flotation of lead (or copper).
According to an aspect of the invention, there is provided a method
for flotation of zinc-containing ore for mixed base metal ore
comprising:
grinding a quantity of mixed base metal ore, said mixed base metal
ore comprising lead-zinc ore and/or copper-zinc ore;
adding water and a frothing agent to the ground ore, thereby
forming a ground ore solution;
adding a lead collector solution and/or a copper collector
solution;
collecting floated lead ore and/or copper ore from the ground ore
solution;
adding a zinc collector, said zinc collector having a chemical
structure according to compound (6):
##STR00004## wherein:
R.sup.1=H, R.sup.2=alkyl, aryl, alkoxy; or
R.sup.1=alkyl, aryl, alkoxy; R.sup.2=H; or
R.sup.1=R.sup.2=alkyl; and
y=2 or 3; and
collecting the zinc-containing ore.
In some embodiments, R.sup.1 and/or R.sup.2 is a C.sub.2-C.sub.12
alkyl, aryl or alkoxy, where appropriate. In other embodiments,
R.sup.1 and/or R.sup.2 is a C.sub.2-C.sub.9 alkyl, aryl or alkoxy,
where appropriate.
The zinc collector may have a chemical structure according to
compound (5):
##STR00005##
wherein x is an integer.
In some embodiments, x may be an integer between 2 and 12, for
example, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 or 12. In other
embodiments, x may be an integer between 2 and 9, for example, 2,
3, 4, 5, 6, 7, 8 or 9. In some embodiments, x may be 2, 3, 5 or
9.
In some embodiments, as discussed below, the zinc collector is in
the form of a water-soluble salt, for example, an amine salt,
although other suitable salts known in the art may also be used
within the invention.
Alternatively, other modifications and/or substitutions may be to
any of the compounds as set forth above that improves the
solubility of the zinc collector compound in water. Such
modifications likely to improve the solubility without affecting
the zinc binding can be determined by one of skill in the art
through routine experimentation and are accordingly considered to
be within the scope of the invention.
In some embodiments, as discussed below, the zinc collector is
added in amount of at least 300 g/tonne of ore.
As discussed below, in some embodiments, the pH of the ground ore
solution is adjusted to below 7 prior to adding the lead collector
or a copper collector solution. For example, the pH may be between
about 6 and about 7 or the pH may be about 6.
In some embodiments, copper sulfate may be added in an amount of
100 g/tonne of ore to the ground ore solution to improve the zinc
recovery process, as discussed below.
According to another aspect of the invention, there is provided a
zinc collector compound, said compound comprising a chemical
structure according to compound (6):
##STR00006## wherein:
R.sup.1=H, R.sup.2=alkyl, aryl, alkoxy; or
R.sup.1=alkyl, aryl, alkoxy; R.sup.2=H; or
R.sup.1=R.sup.2=alkyl; and
y=2 or 3,
for flotation of a zinc-containing ore.
In some embodiments, R.sup.1 and/or R.sup.2 is a C.sub.2-C.sub.12
alkyl, aryl or alkoxy, where appropriate. In other embodiments,
R.sup.1 and/or R.sup.2 is a C.sub.2-C.sub.9 alkyl, aryl or alkoxy,
where appropriate.
In other embodiments, the zinc collector has a chemical structure
according to compound (5):
##STR00007##
wherein x is an integer.
In some embodiments, x is an integer between 2 and 12, for example,
2, 3, 4, 5, 6, 7, 8, 9, 10, 11 or 12. In other embodiments, x is an
integer between 2 and 9, for example, 2, 3, 4, 5, 6, 7, 8 or 9. In
some embodiments, x is 2, 3, 5 or 9.
A Quantitative Structure Activity Relationships modeling approach
using calculated molecular descriptors was extensively used to
select a few potential chemicals for testing from a virtual
database containing thousands of chemicals..sup.1 The approach was
used to select arylhydroxamic acids for the flotation of zinc ores.
Continuation of the efforts in finding a collector for zinc
minerals lead to the selection of 2-(alkylamino)thiols for the
flotation of sphalerite without the use of activation by copper
sulfate as is otherwise necessary in the popular xanthate flotation
schemes currently followed throughout the world.
The basic molecular structure or the chemical class was decided
based on the study of zinc co-ordination sites in various
biological molecules such as zinc finger proteins. In most of the
cases zinc is bound to at least an amine (--NH.sub.2) group and a
thiol (--SH) group. Hence, amino thiol skeleton was chosen as the
potential candidate for selective flotation of zinc minerals.
We synthesized two compounds and used two additional compounds that
are available from Sigma Aldrich. The molecular structures are
given below:
##STR00008##
Compound (1) and compound (4) were purchased from Sigma Aldrich.
Compound (2) and compound (3) were synthesized. As discussed
herein, compound (1) gave the best results.
Compound (2) and compound (3) produced similar but not identical
results. While not wishing to be bound to a particular theory or
hypothesis, we believe that the issue is the lower water solubility
of these compounds, as water solubility decreases with an increase
in molecular chain length.
Surprisingly, compound (4) did not perform well. Again, while not
wishing to be bound to a particular theory or hypothesis, it is
believed that this is due to the crowding near the
mineral-collector binding site. Specifically, the group
--O--(C(CH.sub.3).sub.3) is a bulky group that could create steric
hindrance for surface chelation.
Compounds 1-3 may be represented by a common structure:
##STR00009## wherein "x" is an integer . . . . In some embodiments,
"x" is an integer between 2 and 9. In yet other embodiments, x is
2, 3, 5 or 9.
Alternatively, the N-alkylaminothiol collector may be represented
as follows:
##STR00010## wherein: R.sup.1=H, R.sup.2=alkyl, aryl, alkoxy; or
R.sup.1=alkyl, aryl, alkoxy; R.sup.2=H; or R.sup.1=R.sup.2=alkyl;
and y=2 or 3.
In some embodiments, R.sup.1 and/or R.sup.2 is a C.sub.2-C.sub.12
alkyl, aryl or alkoxy, where appropriate. In other embodiments,
R.sup.1 and/or R.sup.2 is a C.sub.2-C.sub.9 alkyl, aryl or alkoxy,
where appropriate.
As discussed herein, compounds 1, 2, 3, 5 and 6 can be used for
flotation of zinc-containing sulfide and oxide ores as well as
other ores containing zinc.
The invention will now be further elucidated by way of examples.
However, the invention is not necessarily limited by the
examples.
Example 1--Material Used
Ore
A lead-zinc ore containing lead as galena (6-8%), zinc as
sphalerite (20-22%), iron as pyrite (7-9%) and the remaining as
silica (sand) was used in the study.
Auxiliary Chemicals
Sodium cyanide 1% (w/w) in water;
Sodium metabisulfite (MBS) 1% (w/w) in water; Zinc sulfate 1% (w/w)
in water; Copper sulfate 10% (w/w) in water;
Potassium ethyl xanthate (PEX) 1% (w/w) in water; Potassium amyl
xanthate (PAX) 1% (w/w) in water; Methyl isobutyl carbinol (MIBC)
0.1% (w/w) in water; Lime (pH modifier) in water.
Example 2--Methods
Synthesis of Amino Thiols
2-(Alkylamino)ethanethiols of general formula RNHCH.sub.2CH.sub.2SH
are possible to be synthesized by three general methods. The first
one involves the reaction of 2-(alkylamino)ethyl halides with the
hydrosulfides of the alkali metals.sup.2,3. Another method is based
on the nucleophilic substitution of the 2-(alkylamino)ethyl halides
with thiourea followed by an alkaline hydrolysis of the
isothiouronium salts.sup.4,5 and the last method is the
mercaptoethylation of the primary and the amines with ethylene
sulfide.sup.6-8 or other mercaptoethylating agents such as ethyl
2-hydroxyethylthiol-carbonate.sup.8-10, ethyl
2-mercaptoethylcarbonate.sup.9-11 and
ethylenemonothiolcarbonate.sup.12. Another method of
mercaptoethylation using ethylene sulfide is outlined by Brand and
Vahrenkamp.sup.13. In the present invention,
2-(alkylamino)ethanethiols were synthesized by two procedures known
in the art. The two procedures are explained for the synthesis of a
typical compound.
Procedure 1: Synthesis of 2-(octylamino)ethanthiol
Octylamine (11.5 g; 90 mL) in 40 mL toluene was taken in a
round-bottomed flask and heated under reflux. Ethylene sulfide (4.5
g, 75 mmol) in 100 mL toluene was added slowly through a separating
funnel over a period of one hour. The reaction mixture was then
refluxed for twenty hours. The solution was cooled and the toluene
with any unreacted ethylene sulfide was removed by boiling under
reduced pressure using a flash evaporator. The resultant product
was cleaned by passing through a short column of silica gel.
Procedure 2: Synthesis of 2-(otcylamino)ethanthiol
To a stirring solution of 15.5 g of triethylamine in 75 mL water,
silver nitrate solution (12 g in 20 mL water) was added slowly.
Black silver oxide was formed. Octyl amine (11.9 g) was added to
the solution over a period of five minutes. Ethylene sulfide (5 g)
was slowly added to the reaction mixture and the temperature rose
from 25.degree. C. to 40.degree. C. The mixture became yellow,
indicating the formation of a silver complex. The resulting solid
was broken with a glass rod and stirred for two hours. The silver
complex was filtered off and washed with distilled water. The solid
was suspended in 100 mL water and hydrogen sulfide gas was passed
from a Kipp's apparatus with vigorous stirring. After thirty
minutes the precipitated silver sulfide was filtered off and the
solid was washed with ethanol. The washings were collected with the
filtered solution and evaporated in a flash evaporator. The residue
was treated with 100 mL water and extracted with ether. Evaporation
of the ether layer gave 2-(octylamino)ethanethiol.
Some of the 2-(alkylamino)ethanethiols are commercially available
as such or as their ammonium salt. These chemicals are: 1)
2-Aminoethanethiol hydrochloride: CAS Number: 156-57-0 2)
2-(Butylamino)ethanethiol: CAS Number: 5842-00-2 3) tert-Butyl
N-(2-mercaptoethyl)carbamate: CAS Number: 67385-09-5 4)
2-(octylamino)ethanethiol hydrochloride: No CAS Number
available
Example 3--Flotation Tests
As discussed herein, the usual process followed by us was as
follows. The ore was ground in a polyurethane-lined rod mill at 67%
solids so that the rod mill discharge was 80% less than 53 .mu.m
just prior to flotation. 10 mL of sodium metabisulfite solution and
10 mL of zinc sulfate solution were added during grinding. A
prefloat was collected for five minutes using 10 mL of 1% methyl
isobutyl carbinol (MIBC) frother. After the prefloat, the pH was
adjusted to neutral (7 to 7.2). 5 mL of sodium cyanide solution and
additional 5 mL of zinc sulfate solution were added to the pulp.
Then 10 mL of 1% potassium ethyl xanthate (PEX) collector solution
was added and the pulp was conditioned for one minute. Lead ore was
floated as lead-rougher (Pb-R) after adding 10 mL MIBC solution and
opening air at the flow rate of 3 L/min for 5 minutes. After the
Pb-R stage, the copper sulfate solution (12 mL) was added and the
pulp was conditioned for 1 min. This was followed by the addition
of 10 mL of the potassium amyl xanthate (PAX) collector solution
and the pulp was again conditioned for one minute. Sphalerite was
then floated as the zinc rougher (Zn-R) using 10 mL MIBC frother
and 3 L/min air. The float concentrate and the tails samples from
each test were filtered, dried, weighed, carefully homogenized, and
their representative samples were acid-digested, and were analyzed
through Inductively Coupled Argon Plasma Spectrometry (ICAP).
In the instant invention, the above procedure was adhered to for
collecting the lead-rougher, i.e., lead-rougher was collected with
potassium ethyl xanthate (PEX), but potassium amyl xanthate (PAX)
was replaced with the inventive compound/compounds at the
concentrations and pH values mentioned below. Furthermore, except
for the use of the new compounds, all materials were prepared in
ordinary tap water, as is done in the mills, and in concentrations
used in the industry.
Example 4--Results
a) Four 2-(alkylamio)ethanthiols were tested and among them
2-(buylamino)ethanethiol gave the best results.
b) Compound (1) gave the best results at pH 6.
TABLE-US-00001 Zinc pH recovery % Zinc grade 6 25.7 43.5 7 10.3
36.1 8 7.6 30.2 9 2.5 26.7 10 3.3 32.6 10.5 1.5 28.1
The tests were carried out using only 55 .mu.L of the
2-(butylamino)ethanethiol for 350 g of ore.
c) Collector concentration of 300 g/tonne was found to be most
optimal for effective flotation of sphalerite.
TABLE-US-00002 Collector concentration Zinc Pyrite-iron (g/tonne of
ore) recovery % recovery % 200 41.8 45.6 300 70.2 59.9 400 73.8
59.3 500 84.3 47.0
As there is no significant difference between 300 g/tonne and 400
g/tonne
d) Different amounts of copper sulfate from 100 g/tonne to 400
g/tonne were tested and 200 g/tonne gave the best zinc recovery
with low pyrite recovery.
e) Though there is no significant difference in the zinc recovery
on adding various amounts of copper sulfate, the selectivity for
sphalerite increased with an increase in amount of copper sulfate
added. 200 g/tonne was found to give the best zinc recovery at
95.8% with overall sphalerite grade of 45% containing about 3%
pyrite.
TABLE-US-00003 Copper sulfate added Zinc Pyrite-iron (g/tonne of
ore) recovery % recovery % 0 70.2 59.9 100 84.8 46.2 200 95.8 39.1
300 95.3 36.4
Addition of copper sulfate increased the zinc recovery and improved
the grade of the float (lower amount of pyrite in the float
concentrate). Significantly, addition of copper sulfate at more
than 200 g/tonne does not improve the zinc recovery and there is no
significant suppression of pyrite.
f) The 2-(alkylamino)ethanethiols synthesized and tested in the
invention are more selective for zinc than pyrite.
g) The recovery and grade are comparable or slightly better than
those obtained using conventional potassium amyl xanthate collector
with 1 kg of copper sulfate per tonne of ore in the zinc-rougher
stage.
In order to understand the selectivity of the new collectors,
flotation kinetics were studied for the zinc-rougher stage by
collecting float concentrates at various time intervals. The
results are usually plotted as time vs recovery (%). Zinc recovery
obtained under similar conditions on using potassium amyl xanthate
(PAX) and 1 kg of copper sulfate per tonne of the ore was lower.
The time-recovery plots obtained for the use of three different
copper sulfate concentrations are shown in FIGS. 1-3.
Using the flotation kinetics data, a Selectivity Index between
sphalerite and pyrite is calculated for the three amounts of copper
sulfate addition. Selectivity index for a collector is the ratio of
modified rate constant (K.sub.m) for valuable mineral to that for
gangue mineral and modified rate constant (K.sub.m) is the product
of rate constant (k) for flotation kinetics and the maximum
recovery at infinite time (R.sub..infin.).sup.1. The results are
given in the Table below:
TABLE-US-00004 Copper sulfate Selectivity added (g/tonne) K.sub.m
for Sphalerite K.sub.m for Pyrite Index 200 62.9 7.1 8.80 300 61.8
7.9 7.79 400 62.0 9.4 6.62
The results clearly show the higher selectivity for sphalerite at
200 g/tonne and the selectivity is sacrificed on adding more copper
sulfate. Hence, a small amount of copper sulfate is enough to
reactivate the zinc ore suppressed in the lead-rougher stage.
h) The new collector effectively floats sphalerite (zinc) from a
mixed base metal sulfide ore such as a lead-zinc or a copper-zinc
ore without compromising the recovery and grade using only 20% of
copper sulfate required for conventional PAX collector in the
zinc-rougher stage.
i) The compounds are also able to float sphalerite effectively from
a copper-zinc sulfide ore without activation by copper sulfate.
There is no significant difference in the zinc recovery on adding
copper sulfate.
The scope of the claims should not be limited by the preferred
embodiments set forth in the Examples but should be given the
broadest interpretation consistent with the description as a
whole.
REFERENCES
1. Natarajan, R. (2013) Hydroxamic acids as chelating mineral
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